<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .line {
            height: 1px;
            background-color: skyblue;
            transform: scaleY(0.5);
        }
    </style>
</head>
<body>
    <!-- 
        定义一条高为1px的div元素
        然后通过transform属性以及scaleY(0.5)将其缩放至0.5倍
     -->
    <div class="line"></div>
</body>
</html>